Bright nickel electroplating



United States Patent O 3,296,103 BRIGHT NICKEL ELECTROPLATING Frank Passal, Detroit, Mich, assignor to M 8: T Chemicals Inc., New York, N.Y., a corporation of Delaware N Drawing. Filed Feb. 24, 1964, Ser- No. 347,046 10 Claims. (Cl. 204-49) This invention relates to electroplating nickel and more particularly to the electrodeposit-ion of bright nickel.

Nickel electrodeposits as plated from Watts, high chloride, fluoborate, etc. type baths are not bright When plated in thicknesses substantially greater than those of very thin strike or flash coatings. Such deposits do not increase in luster with increasing thickness but rather decrease in brightness until dull matte deposits are obtained. To obtain thick bright deposits from such baths, it is necessary to add certain additives, commonly of organic nature, which assist in producing highly lustrous deposits with :good rate of brightening. It is a common characteristic of such so-called bright nickel plating baths that the deposits tend to increase in luster With increasing thickness. A particular advantage of these bright nickel baths is that bright deposits can be obtained on basis metals which have not been polished or which do not have a high starting luster, within reasonable specification thicknesses of nickel. Other concomitant advantages such as leveling or the ability of the deposits to fill in pores, scratches, or other superficial defects of the basic metal, may also be obtained.

Addition agents useful as brighteners in nickel plating baths are generally divided into two classes on the basis of their predominant function. Primary brighteners are materials used in very low or relatively low concentration, typically 0.002-0.2 ig./l., which by themselves may or may not produce visible brightening action. Those primary brighteners which may exhibit some brightening effects When used alone generally also produce deleterious side effects such as reduced cathode efficiency, poor deposit color, deposit brittleness and exfoliation, very narrow bright plate range, or failure to plate at all on low current density areas. Secondary brighteners are materials which are ordinarily used in combination with primary brighteners but in appreciably higher concentration than that of the primary brighteners, typically 1 g./l. to 30 g./l. These materials, by themselves, may produce some brightening or grain-refining efiects, but the deposits are not usually mirror bright and the rate of brightening is usually inadequate.

Ideally, when primary and secondary brighteners of properly chosen and compatible nature are combined it is possible to obtain, over a Wide current density range, ductile, leveled deposits which exhibit a good rate of brightening. The rate of brightening and leveling may vary in degree depending on the particular cooperating additives chosen and their actual and relative concentrations. A high degree of rate of brightening and leveling is generally desirable, particularly where maximum luster is desired with minimum nickel thicknesses. The concentrations of the secondary brighteners may usually vary within fairly wide limits. The concentrations of the primary brighteners rnust usually be maintained within fairly narrow limits in order to maintain desirable properties including good ductility, adequate coverage over low current density areas, etc. Any bright nickel system which can be rendered more tolerant to fluctuations in primary brightener concentrations will have obvious advantages, particularly since the low concentration of primary brighteners and the intrinsic chemical nature of some make strict control by chemical analysis difficult. A primary brightener which can be used over a Wide range of concentration is of great value in bright nickel plating.

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It is an object of this invention to provide improved nickel plate .by use of a new class of superior primary brighteners. It is a further object of this invention to provide an efl'icient process for electrodepositing bright and smooth nickel deposits. Another object of this invention is to provide bath compositions for nickel plating from which bright nickel electrodeposi-ts are obtained. Other objects of this invention may be apparent to those skilled in the art on inspection of the following description. I

In accordance with certain of-its aspects, the process of this invention comprises elect-rodepositing nickel from an aqueous nickel electroplating bath containing a secondray brightener end, as a primary brightener, a compound having a cation of the structure wherein A and B may each be selected from the group consisting of hydrogen, carboxamido OOHN acetyl COCH and carbomethoxy --COOCH and at least one of A and B is other than hydrogen.

Typical compounds of this class which may be efiective as primary brighteners are the following:

TABLE I (A) 3-carboxamido N-pr-opargyl pyridinium bromide (B) 3-acetyl N-propargyl pyridinium bromide (C) 3-carbomethoxy N-propargyl pyridinium bromide (D) 4-carboxamido N-propargyl pyridinium bromide (E) 4-acetyl N-propargyl pyridinium bromide (F) 4-carbomethoxy N-propargyl pyridinium bromide The novel class of primary brighteners of this invention when used in combination with (a) suitable secondary brighteners or (b) secondary and secondary auxiliary brighteners, may give brilliant, nickel deposits which have excellent ductility, good low current density coverage and luster, good rate of brightening, and good leveling characteristics. It is a particular feature of this invention that the preferred novel primary brighteners may be used over a Wide range of concentration with attainment of good low current density coverage and ductility of the deposits.

Another outstanding advantage is that these novel primary brighteners can withstand long electrolysis without build-up in the nickel plating 'bath of harmful decomposition products. Prior art nickel plating techniques may include the use of a number of acetylenically quaternized nitrogen heterocyclic compounds as primary brighteners; but they either produce inadequately lustrous deposits or are difiicult to synthesize in high purity and yield; they have limited compatibility with the more commonly used additives. The compounds of this invention, including the 3- and 4-substituted propargyl pyridinium quaternaries, do not have these defects and in addition exhibit low rates of consumption. The 3- and 4-substituent groups of this invention are specifically chosen. Other groups in these positions either make the quaternaries difiioult or impossible to synthesize or result in compounds ineffective as primary brighteners.

The primary brighteners of this invention may be used in concentrations of 0.005 g./l. to 0.10 g./l., the particular concentration chosen depending on the particular types and concentration of secondary and secondary auxiliary brighteners used, and also on such factors as the concentrations of nickel sulfate, nickel chloride, and boric acid; operating conditions with respect to temperature and degree of agitation; degree of luster, rate of brightening and leveling desired; and the finish of the basis metal. It is preferred to use between 0.01 g./l. and 0.05 g./l.

Secondary brighteners (typically present in amount of 1 g./l. to 75 g./l., and preferably 1 g./l. to g./l.) which are useful in combination with the primary brighteners, are generally aromatic sulfonates, sulfonamides or sulfimides which may include such substituted aromatic compounds as 'l,3,6-naphthalene trisulfonate, sodium or potassium salts of saccharin, sodium or potassium salts of orthosulfobenzaldehyde, benzene sulfonamide, benzene mono-sulfonate, etc. For use in high chloride type nickel plating baths, a preferred secondary brightener may be a sodium or potassium salt of sulfonated dibenzothiophene dioxide, prepared by sulfonating diphenyl' with fuming sulfuric acid (20% oleum) for about 2 hours, isolating the reaction product, and neutralizing. The predominant reaction product is believed to be the compound containing three sulfonic acid groups, together with some monoand di-substituted components. The secondary brighteners are generally characterized by having at least one sulfone or sulfonic acid group attached to a nuclear carbon of a homocyclic aromatic ring.

Aromatic secondary brighteners such as sodium-Z-propene-l-sulfonate; sodium 3-chloro-2-butene-l-sulfonate; mixed isomer of sodium-2-butene-2-hydroxy-l-sulfonate and sodium-2-butene-l-hydroxy-Z-sulfonate, prepared by reacting butadiene monoxide with sodium sulfite; or phenyl propiolarnide may be used in conjunction with the secondary brightener or brighteners.

Conventional baths and processes for electroplating bright nickel are described in Principles of Electroplating and Electroforming, Blum and Hogaboom, pages 362-381, revised third edition, 1949, McGraw-I-Iill Book Co., Inc., New York; and in Modern Electroplating, edited by A. G. Gray, The Electrochemical Society, 1953, pages 299-355. The control and operating conditions, including the concentration of the bath ingredients, pH, temperature, cathode current density, etc., of these conventional baths are generally applicable to the present invention. Practically all baths for electroplating bright nickel contain nickel sulfate; a chloride, usually nickel chloride; a buffering agent, usually boric acid; and a wetting agent, e.g. sodium lauryl sulfate, sodium lauryl ether sulfate, or sodium 7-ethyl-2-methyl-4-undecanol sul fate. Such baths include the well-known Watts bath and the high chloride bath. Other baths may contain, as the source of the nickel, a combination of nickel fluoborate with nickel sulfate and nickel chloride, or a combination of nickel fluoborate with nickel chloride.

'Typical Watts-type baths and high chloride baths are Nickel sulfate 200 g./l. to 400 g./l. Nickel chloride g./l. to 75 g./l. Boric acid 30 g./l. to 50 g./l. Temperature 38 C. to 65 C. Agitation Mechanical and/ or air or solution pumping, etc. pH 2.5 to 4.5 electrometric.

TABLE III High chloride baths Nickel chloride 150 g./l. to 300 g./l. Nickel sulfate 40 g./l. to 150 g./l Boric acid 30 g./l. to 50 gl. Temperature 38 C. to 65 C. Agitation Mechanical and/ or air or solution pumping, etc. pH 2.5 to 4.5 electrometric.

Best plating results are usually achieved in the electrodeposition process when there is used a method of preventing the thin film immediately adjacent to the cathode from becoming depleted in cation content. This is desira- 4 bly accomplished by agitation, such as by air agitation, solution pumping, moving cathode rod, etc.

For the purpose of giving those skilled in the art a better understanding of the invention, illustrative examples are given. In each of the examples, an aqueous acidic nickel-containing bath was made up with the specified components. Electrodeposition of nickel was carried out by passing electric current through an electric circuit comprising a nickel anode and a sheet metal cathode, both immersed in the bath. The baths were agitated, usually by a moving cathode. Bright electrodeposits were obtained in all the tests included herein as examples.

In Examples 1 through 14 inclusive, the following standard bath was used as a base solution:

Nickel sulfate, g./l. 300

Nickel chloride, g./l. 60 Boric acid, g./l. Sodium lauryl sulfate, g./l. 0.25

The primary brighteners are identified from Table I, supra. The secondary brighteners which are used in the following examples as noted in Table IV infra, include:

TABLE IV Secondary brighteners (G) o-benzoic sulfirnide (Na salt) (H) di'benzene sulfonamide (I) N,N bis(phenylsulfonyl) 4,4-diphenyl disulfonamide (J sulfonated dibenzothiophene dioxide The auxiliary secondary brighteners which are used in the following examples as noted in Table V infra include:

TABLE V Auxiliary secondaly brighteners (K) sodium-3-chloro-2-butene-l-sulfonate (L) sodium allyl sulfonate In the following examples asd signifies amperes per square decimeter.

TABLE VI Example No. Additive Amount, 0 D asd Tsnp 5. In Examples 15-18 inclusive, the following standard bath was used as a base solution:

Nickel chloride, g./l. 250

Nickel sulfate g./1. 45 Boric acid g./l 45 Sodium lauryl sulfate, g./l a. 0.25

TABLE VII Example N o. Additive Amolilmt, CD asd Tergp The foregoing examples illustrate specific baths and processes. It is understood that the compositions and conditions may be varied. Although the potassium and sodium salts were most often used and are preferred, they may be partially or completely replaced by such other salts as nickel, magnesium, etc. salts.

The nickel electrodeposits obtained from 'baths utilizing the novel brightener combination are advantageous in that mirror-bright lustrous electrodeposits having a high degree of ductility are obtained over a wide range of cathode current densities. The bright nickel electrodeposits are preferably plated on a copper or copper alloy basis metal. However, they may be electrodeposited directly on such metals as iron, steel, etc.

The novel primary brighteners of this invention may be prepared by the following reaction:

consisting of hydrogen, carboxamido CONH acetyl COCH and carbomethoxy COOCH -at least one of A and B being other than hydrogen, and wherein X is an anion, preferably halogen. Thus for example, the heterocyclic compound may be B-substituted pyridine or 4-substituted pyridine viz (l C 1 H Typical reactants N which may be employed in the process of this invention may include:

S-carboxamido pyridine (nieotinamide) 3-carbomethoxy pyridine (methyl nicotinate) 3-acetyl pyridine Typical reactants which may be employed in the process of this invention may include:

4-carboxamido pyridine (isonicotinamide) 4-carbomethoxy pyridine (methyl isonicotinate) 4-acetyl pyridine Typical reactants HC=CCH X which may be employed include those wherein X may be halogen. Most preferred because of ease of reaction and availability may be propargyl bromide, HCECCH2BT.

It will be apparent to those skilled in the art that inertly substituted reactants may be employed.

The reaction of the heterocyclic compound and the acetylenic halide may typically be effected under mild conditions, preferably in the presence of solvent. The reaction may occur readily in high yield typically at room temperature with slight warming usually occurring at the beginning of the reaction. The product generally may be a well-defined crystalline solid which may be recovered from the reaction system as by filtration followed by washing with appropriate solvent such as acetone. Recrystallization is generally unnecessary and the product may be easily air-dried.

The reaction may be carried out in the presence of inert solvents including preferably acetone, dimethylform amide, or mixtures thereof. r

Carrying out the reaction may include dissolving one mole of the heterocyclic compound in an excess of solvent sufiicient to dissolve the compound. Typically the solvent may be present in amount of 3-4 times the weight of the compound. To this mixture there may :be added at least one mole and preferably 11.5 moles of acetylenic halide, preferably propargyl bromide. The mixture may be allowed to stand at room temperature for two hours to several days depending on the particular product being prepared.

Conversion of the novel compounds to other novel compounds in practice of this invention may be effected by the reaction thereof with e.g. soluble silver salts of desired anions such as acetate, sulfate, perchlorate, methosulfate, etc. Typically this reaction may be effected in aqueous medium by mixing equivalent amounts of the reactants and filtering off the insoluble silver halide, e.g.

CONH2 AgOOOCI-I;

N- OH2CECH CONHz AgBr h rlflorrrozorn b00011.- Preparation of the novel compounds of this invention may be further illustrated by the following illustrative specific Examples 19-21:

Example 19.-Synthesis 0 3-carboxumid0 N-propargyl pyridinz'um bromide 35 g. nicotinamide, ml. dimethylformamide, and 25 ml. propargyl bromide were allowed to stand at room temperature for 68 hours. The crystalline product was filtered off, washed with acetone and air-dried. Yield 68 g. (94% )M.P. 187190 C. (by melting point as determined in the Fisher-Johns apparatus).

7 Example 20.-Synthesis of 3-carbomethoxy N-propargyl pyridinium bromide 10. g. of methylnicotinate, 25 m1. dimethylformamide, and 15 ml. propargyl bromide were allowed to stand at room temperature for 3 hours. The crystalline product was filtered off, washed with acetone and air-dried. Yield 15.55 g. (83%)-M.P. 135-136 C. (Fisher-Johns).

Example 21 .-Synthesis of 4-acetyl N-propargyl 'pyria'inium bromide 10.8 g. 4-acetylpyridine, 25 ml. dimethyltormamide, and ml; propargyl bromide were allowed to stand at room temperature for 25.5 hours. To the reaction mixture 100 ml. acetone were added and the crystalline product was filtered 01f, washed with acetone and dried in a desiccator. Yield 18.1 g. (85%)-'M.P. [darkens 195 C. melts with decomposition about 280 C.] (Fisher- Johns).

Although this invention has been illustrated by reference to specific examples, numerous changes and modifications thereof which clearly fall within the scope of the invention will be apparent to those skilled in the art.

I claim:

1. The process for electrodepositing nickel which comprises electrodepositing nickel from an aqueous nickel electroplating bat-h containing a secondary'brightener and,

as a primary brightener, an eifect-ive amount of a compound having a cation of the structure I l T- CHrC/ECH wherein A and B are each selected from the group consisting of hydrogen, carboxamido -CONH acetyl COCH and carbomethoxy -COOCH and at least one of A and B is other than hydrogen.

2. The process claimed in claim 1 wherein said primary brightener is present in amount of 0.005 g./l. to 0.10 g./l.

3. The process claimed in claim 1 wherein said compound is 3-carboxamido N-propargyl pyridiniumbromide.

4. The process claimed in claim 1 wherein said compound is 3-carbomethoxy N-propargyl pyridinium bromide.

5. The process claimed in claim 1 wherein said compound is 4-acetyl N-propargyl pyridinium bromide.

6. An aqueous electrolytic bath containing soluble 7 8 salts for the electrodeposition of nickel and containing as a primary brightener, an effective amount of a compound having a cation of the structure N CHr-CECH wherein A and B are each selected from the group consisting of hydrogen, carboxamido CONH acetyl COOH and carbomethoxy COOCH and at least one of A and B is other than hydrogen.

7. An "aqueous electrolytic bat-h containing soluble salts for the electrodeposition of nickel as claimed in claim 6 wherein said primary brightener is present in amount of 0.005 g./l. to 0.10 g./l.

8. An aqueous electrolytic bath containing soluble salts for the electrodeposition of nickel as claimed in claim 6 wherein said primary brightener is 3-carboxamido N- pr-opargyl pyridinium bromide.

9. An aqueous electrolytic hathcontaining soluble salts for the electrodeposition of nickel as claimed in claim ,6 wherein saidprimary brightener is 3-carbomethoxy N- propargyl pyridinium bromide.

10. An aqueous electrolytic bath containing soluble salts for the electrodeposition of nickel as claimed in claim 6 wherein said primary brightener is 4-acetyl N- propargyl pyridinium bromide.

References Cited by the Examiner UNITED STATES PATENTS 2,647,866 8/1953 Brown 204-49 2,749,349 6/1956 Cislak 260-290 2,938,033 5/1960 Stehrn-an 260-290 3,006,822 10/ 1961 Todt 204-49 3,054,733 9/1962 Heiling 204-49 3,170,854 2/1965 Kroll 204--49 3,170,855 2/1965 Kroll 204-49 3,218,244 11/1965 Passal et al. 204-49 FOREIGN PATENTS 1,066,068 9/ 1959 Germany.

638,868 6/ 1950 Great Britain.

JOHN H. MACK, Primary Examiner.

MURRAY TILLMAN, G. KAPLAN,

' Assistant Examiners. 

1. THE PROCESS FOR ELECTRODEPOSITING NICKEL WHICH COMPRISES ELECTRODEPOSITING NICKEL FROM AN AQUEOUS NICKEL ELECTROPLATING BATH CONTAINING A SECONDARY BRIGHTENER AND, AS A PRIMARY BRIGHTENER, AN EFFECTIVE AMOUNT OF A COMPOUND HAVING A CATION OF THE STRUCTURE 